The primary purpose of this proposal is to examine the role of class II MHC antigen and its associated molecules (H-2M and Ii) in allogeneic and/or xenogeneic transplantation involving keratinocytes and islet cells. These studies stem from the applicants' observation that keratinocytes isolated from class II MHC defective mice failed to prime for an allogeneic response from the host. These studies have motivated an examination of the role of other proteins in allogeneic transplant rejection or acceptance. Specifically, the investigators wish to test three mice strains: mice defective in the IA(b)[beta]gene, the H-2M molecule (which is necessary for peptide loading onto class II MHC proteins) and CIITA, a master transcriptional regulator essential for trans-activation of class II MHC genes, Ii chain, and the H-2M genes. Using keratinocytes and islet cells derived from these three mice, the applicants wish to test their acceptance as allografts. In addition, they wish to test if pre- transplantation with keratinocytes that are defective in class II MHC antigens can result in tolerance induction which can enhance the successful implant of allogeneic islet cells. Accordingly, the following aims will be pursued. First, immunologic priming by IA(b)[beta](-/-), H-2M(-/-), and CIITA(-/-) keratinocytes will be compared. The capacity of cells isolated from these animals to prime an allo- and xenoresponse will be assessed. Secondly, the acceptance of islet allografts from IA(b)[beta](-/-), H-2M(-/-), and CIITA(-/-) animals will be compared to grafts from wild type controls. The capacity to restore normal glycemia will be examined. Finally, the failure of keratinocytes from IA(b)[beta](-/-) allografts suggests that these cells may have caused immunologic tolerance. Direct studies to examine if this is the case are planned. An extension of these experiments will be to determine if mice transplanted with IA(b)[beta](-/-) keratinocytes are more tolerant of I(A(b)[beta](-/-) allogeneic islet cells. Similarly, if the experiments with H-2M(-/-) or CIITA(-/-) are encouraging, they also will be tested to determine if they can induce prolonged acceptance of islet cells. Together these experiments should shed light on the biological function of class II antigens as well as molecules involved in class II presentation in transplants that are relevant to a large proportion of patients with severe unhealed wounds, burns, or diabetes.